This invention relates to a method of forming a mine support to a mine support so formed, and to elements for use in its construction.
It is well known to form support structures such as roadways, canals or river or bank linings and the like from a material having a honeycomb structure i.e having a plurality of compartments or cells divided by dividing walls, each compartment or cell being filled with a suitable filler material. Examples of such materials for use in the support structure Hyson-Cells from M and S Technical Consultants and Services (Proprietary) Limited, Geoweb from Presto Products Company, Tenweb from Tenax Corporation, Armater from Crow Company, Terracell from Webtech Inc, Envirogrid from Akzo Nobel Geosynthetics Co, and Geocells from Kaytech.
This elongate tube of a flexible plastics material has also been used as a mine support capable of bearing a compression load as disclosed in South African Patent No 86/0510.
However, there is always a need for new methods of utilising this tube material.
According to a first aspect of the invention there is provided a method of forming a mine support capable of bearing an axial compressive load, the method comprising the steps of:
(1) providing an outer container arranged in use to define a base;
(2) locating within the container a tube of a flexible material divided by dividing walls of a flexible material into an array of compartments or cells running the length of the tube, the compartments being arranged in rows and columns so that the tube divided by the dividing walls has a honeycomb structure, with a first end of the tube positioned in use on the container base and a second end of the tube above the first end of the tube;
(3) filling one or more of the compartments at or near the centre of the tube with a first load bearing material to form a pillar with a load bearing capability in or near the centre of the tube; and
(4) filling the remainder of the compartments of the tube with a second material having no or a lower load bearing capability than the first load bearing material, to form the mine support.
The outer container may be a bag or a box or the like.
When the outer container is a bag it may be a bag conventionally used in the manufacture of mine supports and may be of any size or shape to suit a particular stope. The term xe2x80x9cbagxe2x80x9d includes those large bags known as paddocks.
The bag may be woven or non-woven, water impermeable or permeable and made from any suitable material. Examples are polypropylene or the like, or a plastic which is designed to weep. The bag typically includes at least one inlet for introducing filler material into the tube and the bag.
When the outer container is a box, it may be a rigid or semi-rigid box, which is designed to remain part of the mine support when formed, or to disintegrate. For example the box may be a cardboard box.
The cross-sectional size of the compartments in the tube may vary. For example the cross-sectional size of the compartments at or near the centre of the tube may be smaller than the cross-sectional size of the remainder of the compartments. The cross-sectional size of a compartment is the cross-sectional area thereof at right angles to the axis of the compartment.
The mine support may comprise two or more tubes located side by side in the container.
For example, the mine support may comprise two tubes located adjacent opposed ends of the container.
In this version of the invention, the two tubes are spaced apart in the outer container so that a compartment is defined between the two tubes, the compartment being filled with the second material in step (4).
The mine support may also comprise two or more tubes located one on top of another in the container, the compartments in each tube being of the same cross-sectional size, or the compartments in each tube being of different cross-sectional size.
For example, the mine support may comprise three tubes located one on top of another, with the compartment in the first tube on the base in use having a first cross-sectional size, the compartments in the next adjacent second tube having a second cross-sectional size smaller than the cross-sectional size of the compartments in the first tube, and the compartments in the next adjacent third tube having a third cross-sectional size smaller than the cross-sectional size of the compartments in the second tube.
A sheet of a mesh material or the like may be located between each of the tubes located on the top of another, to reinforce the mine support.
The use of compartments with different cross-sectional sizes is described in more detail in co-pending application PCT/IB 99/00967 which is incorporated herein by reference.
Each tube is preferably secured inside the container, for example by attaching the corners of each tube to the container. In one version, a simple tab or string is provided at each corner of each tube for attaching the tubes to the relevant position of the container.
Alternatively, each tube may be secured inside the container by means of a series of flexible strings or rigid stays located through suitable rows and columns of compartments generally at or near the edges of each tube, which flexible strings or rigid stays are attached to the container or to fixed objects to support the tube with the first end of the tube on the base and the second end of the tube above the first end.
Thus, for example, when a tube is substantially rectangular in plan view, a string or a stay may be located in at least a row or a column of compartments at or near each of the four edges of the tube.
The use of flexible strings or rigid stays to support a tube in position is described in more detail in co-pending application PCT/IB 99/00965, which is incorporated herein by reference.
Further alternatively, the outer walls of the tube may be sufficiently rigid so that the tube is self-supporting.
The tube and the dividing walls may be made from any suitable flexible material. Although the material must possess some degree of flexibility, the degree of flexibility may range from very flexible up to semi-rigid. The flexible material may be for example a plastics material such as for example a co-extruded or a bi-axially extruded plastics material; a plastics mesh material; a plastics laminate material such as for example a laminate of a plastics material and a metallic material or a textile material; a metallic material; a woven or non-woven textile material; a paper or cardboard material; and the like.
The flexible material is preferably a suitable plastics material.
Each tube may have any suitable height and any suitable compartment size. For example, the height of the tube may range from 50 mm to 10 m and each compartment may have a wall length of from 5 mm up to 4 m.
The tube may be shaped, e.g by cutting the compartments in one or more rows or columns at an angle to fit into a desired space, e.g a sloping stope or the like.
Generally, the tube is located with the second end of the tube above the first end of the tube so that a second end of each compartment is substantially directly above a first end of the compartment, i.e the axes of the compartments in the tube are substantially vertical. However, the tube may also be located with the second end of the tube above the first end of the tube so that a second end of each compartment is not directly above a first end of the compartment, i.e the axes of the compartments are at an angle to the vertical. This may be achieved by cutting the compartments at an angle, or by manufacturing the compartments at an angle. This may assist in retaining the first load bearing material and the second material in the compartments.
The compartments in the tube may have any suitable cross-section, such as triangular, square, hexagonal or octagonal, but preferably have a square cross-section, i.e each compartment is defined by four walls of substantially equal length.
A wall or walls of each compartment may include one or more hollow protrusions or one or more hollow recesses or both, for interlocking of adjacent compartments. This is described in more detail in co-pending application PCT/IB 99/00964 which is incorporated herein by reference.
The walls of the tube and the dividing walls may include one or more holes or apertures so that filler material can flow from one compartment to another.
In another embodiment, the or each tube may be so designed as to provide a path for circulating a fluid from a first end to a second end of the tube. In this case, each tube will include first flow means at or near the first end of the tube, and either in the dividing walls between the first and second rows and between the third and fourth rows and between each succeeding pairs of rows, or in the dividing walls between the second and third rows and between the fourth and fifth rows and between each succeeding pair of rows; and second flow means at or near the second end of the tube, and either in the dividing walls between the second and third rows and between the fourth and fifth rows and between each succeeding pairs of rows, or in the dividing walls between the first and second rows and between the third and fourth rows and between each succeeding pairs of rows, so that the first flow means and the second flow means alternate.
In this way, a fluid such as mine water may be circulated through the tube, e.g mine water introduced through a fluid inlet at a first end of the tube flowing either up or down the compartments in the first row, through the first or second flow means between the first and second rows, and then down or up the compartments in the second row, through the second or first flow means between the second and third rows, and so on until the water reaches the fluid outlet. This is possible even though certain of the compartments at or near the centre of the tube are filled with the first load bearing material, in that other compartments will be filled with the second material, which permits the flow of the water therethrough.
Apparatus for circulating a fluid as discussed above, is described in more detail in co-pending application PCT/IB 99/01396 which is incorporated herein by reference.
The first load bearing material is typically formed of cementitious grout, crusher sand or cemented slimes or tailings, or the like so that the central pillars have sufficient load bearing capabilities.
The second material may have no load bearing capability, e.g it may be a filter material as described in more detail below, or may have a lower load bearing capability than the first load bearing material.
The second material, when it is to be load bearing, is typically back fill or mine slimes or tailings or similar material having a much lower load bearing capability, or a foamed material to help control of the collapse of the mine support in use.
As mentioned above, the second material may also be a filter material such as for example lime or limestone powder, rocks or blocks, to neutralise mine water flowing therethrough; activated carbon or wire wool for neutralising components in the mine water; pebbles or stones; sand; and the like.
In a further embodiment of the invention, a side of the mine support may incorporate a blast curtain. The blast curtain may be releasably or permanently attached to the mine support, i.e to an outside wall of the outer container.
In a further embodiment of the invention, one or more reinforcing straps or rings or the like may be located around either the outside of the tube or tubes inside the outer container, or around the outside of the outer container, to support the mine support in use.
According to a second aspect of the invention there is provided a mine support formed as described above.
According to a third aspect of the invention there is provided a mine support unit comprising an outer container having at least one filler port or inlet and defining a base in use and a tube of a flexible material divided by dividing walls of a flexible material into an array of compartments or cells running the length of the tube, the compartments being arranged in rows and columns so that the tube divided by the dividing walls has a honeycomb structure, with a first end of the tube positioned in use on the outer container base and a second end of the tube above the first end of the tube, the unit being adapted to receive in use filler material to form a mine support, as described above.